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Valve mechanism of internal combustion engine

Inactive Publication Date: 2003-12-11
HITACHI LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, due to an inherent construction, the above-mentioned known valve mechanism tends to exhibit a non-negligible inclination or lurching of the cam shaft particularly when the intake valves are under their opening stroke.
As is known, such inclination brings about a development of uneven wearing of bearing portions of the cam shaft.

Method used

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  • Valve mechanism of internal combustion engine
  • Valve mechanism of internal combustion engine
  • Valve mechanism of internal combustion engine

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0025] Referring to FIGS. 1, 2 and 3, particularly FIG. 1 of the drawings, there is shown but partially a valve mechanism 100 of the present invention.

[0026] As will become apparent from the following, valve mechanism 100 of the first embodiment is constructed to incorporate with an internal combustion engine of a type having two intake valves for each cylinder.

[0027] As shown in FIG. 1, a cylinder head 1 of the engine has two intake valves 2 and 2 for each cylinder, which are slidably held through valve guides (not shown). A drive shaft 3 extends along a longitudinal axis of the engine. A hollow cam shaft 4 is coaxially and rotatably disposed about drive shaft 3. A cylindrical outer surface of drive shaft 3 is denoted by 3a. A drive cam 5 is fixed to drive shaft 3 at a position near an end of cam shaft 4. Cam shaft 4 has at both end portions 4a and 4b thereof respective swing cams 7A and 7B which are integral thereto. Swing cams 7A and 7B are in contact with valve lifters 6 and 6 a...

second embodiment

[0059] Referring to FIG. 5, there is shown a valve mechanism 200 of the present invention.

[0060] In this second embodiment, valve mechanism 200 is constructed to incorporate with an internal combustion engine of a type having one intake valve for each cylinder. As shown, cam shaft 4 has a length shorter than that in the first embodiment 100, and a swing cam 7 is integrally mounted on one end 4a of cam shaft 4. Journal portion 4c is formed on the other end 4b of cam shaft 4 and received in bearing 10. Like in case of the first embodiment 100, the thickness of first cylindrical clearance C1 is smaller than that of second cylindrical clearance C2.

[0061] Accordingly, substantially the same advantages as those of the first embodiment 100 are obtained in this second embodiment 200.

[0062] Referring to FIGS. 6, 7, 8 and 9, there are shown valve mechanisms 300, 400, 500 and 600 of third, fourth, fifth and sixth embodiments of the present invention.

[0063] Since these embodiments are similar t...

third embodiment

[0064] In FIG. 6, there is shown valve mechanism 300 of the

[0065] In this third embodiment, the height L2 of the cam nose portion 7b of swing cam 7B is greater than the height L1 of the cam nose portion 7b of swing cam 7A.

[0066] As is seen from FIG. 2, the height L of the cam nose portion 7b is the height of a top of the cam nose portion 7b from the cylindrical outer surface of cam shaft 4.

[0067] Under a valve opening stage of valve mechanism 300, a downward force is applied to one end portion 4a of cam shaft 4 and thus first cylindrical clearance C1 permits a diametrically center position P1 of cam shaft 4 at the end portion 4a to be shifted downward by a distance of .DELTA. / 2. Upon this, a diametrically center position P2 of cam shaft 4 at the other end portion 4b is shifted upward by a distance of .DELTA. / 2. Thus, the two intake valves 22 and 23 are subjected to a lift difference by an amount of .DELTA..

[0068] In this third embodiment 300, the following equation is established:

L2...

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Abstract

A drive shaft is synchronously rotated with a crankshaft of an internal combustion engine. A cylindrical hollow cam shaft is rotatably disposed about the drive shaft keeping a first cylindrical clearance therebetween. The cam shaft is formed with at least one cam that actuates an engine valve for opening and closing the same. A bearing bears a given portion of the cam shaft keeping a second cylindrical clearance therebetween. A movement transmitting mechanism transmits a torque of the drive shaft to the cam shaft while converting a rotation movement of the drive shaft to a swing movement of the cam shaft. The thickness of the first cylindrical clearance is smaller than that of the second cylindrical clearance.

Description

[0001] 1. Field of Invention[0002] The present invention relates in general to valve mechanisms of an internal combustion engine, and more particularly to the valve mechanisms of a type that varies a valve lift characteristic of an intake or exhaust valve of the engine in accordance with an operation condition of the engine.[0003] 2. Description of Related Art[0004] Hitherto, various valve mechanisms of an internal combustion engine have been proposed and put into practical use. One of them is disclosed in Japanese Laid-open Patent Application (Tokkai) 2001-55915. For clarifying the present invention, the valve mechanism of the application will be briefly described in the following.[0005] The valve mechanism is incorporated with an internal combustion engine of a type having two intake valves for each cylinder, and comprises a drive shaft driven synchronously by a crankshaft of the engine, an eccentric drive cam mounted to the drive shaft to rotate therewith, and a cylindrical hollo...

Claims

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Application Information

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IPC IPC(8): F01L1/04F01L1/14F01L13/00
CPCF01L1/022F01L2101/00F01L2013/0073F01L13/0026F01L2301/00
Inventor MIYAZATO, YOSHIAKINAKAMURA, MAKOTO
Owner HITACHI LTD